In the Macross Zero OVA the Sukhoi/Israel Aircraft Industries/Dornier SV-51 was the only variable fighter developed by the Anti-U.N. forces. It can transform into battroid (giant robot), GERWALK and fighter (jet) modes.
The SV in its name actually stands for "Sukhoi Variable" (or "Slayer Valkyrie" according to some other sources).
Like the VF-0 Phoenix, the SV-51 is an advanced trial production model equipped with conventional engines, a proof-of-concept craft developed and pressed into service before planned variable fighters with thermonuclear turbine engines. It can only fly in an atmosphere and is not a space travel-capable aerospace fighter like the later VF-1. A variant called SV-52 with thermonuclear reaction engines was also researched but wasn't mass produced by the Anti-U.N. forces.
The SV-51 armaments included gun pods, missiles, and other ordinance. The mecha was also capable of being launched from underwater. The fighter design was similar to that of the VF-0, but its transformation mechanism was more complicated and took longer to complete. The SV-51 also had canards and tailplanes. Its wing was narrow and relatively unswept.
Since this mecha appeared a whole year before the events of Choujikuu Yousai Macross, many Macross fans have speculated that the remaining units were seized by the U.N. Spacy and used for variable fighter research as well as aerial defense against the Zentradi during Space War I (like they did with the Anti-U.N. Octos mecha, according to the Macross Chronicle). The SV-52 variant with reaction engines was also supposedly produced in limited numbers by the U.N. Spacy after the Anti-U.N. forces were defeated.
